1. Field
The present disclosure relates generally to aircraft and, in particular, to a method and apparatus for a fuel barrier within a wing. Still more particularly, the present disclosure relates to a method and apparatus for managing deflections in an aircraft wing fuel tank.
2. Background
Fuel tanks in some aircraft are contained within the aircraft structure that has been sealed to allow fuel storage. An example of this type is the “wet wing” commonly used in larger aircraft. Since these tanks are part of the aircraft structure, the tanks are designed to meet the structural integrity requirements as well as function of fuel tanks. Large transport aircraft may store fuel in the wings and/or tail of the aircraft. This configuration reduces the weight and complexity as compared to a bladder system.
A fuel barrier may be located between wing ribs and wing panels for fuel containment at fuel tank boundaries in an aircraft. In a wet wing, every joint and fastener along the fuel tank boundary may be sealed to prevent fuel leaking or seeping to the exterior. The sealant may conform to expansion and contraction due to temperature changes. The sealant retains its sealing properties when submerged in fuel, and when left dry for long periods of time. The weight or dynamic loading of the fuel deflects the wing rib relative to the wing stringer. The deflection may cause the sealant to crack when exposed to −65° F. The cracks may allow fuel to leak across the tank boundary. Working with this sealant can be difficult. For example, replacing old sealant inside a small wing tank can be particularly difficult if the old sealant needs to be removed in addition to installing a new sealant.
The stringer may be an enclosed cross section, similar to a hat stringer. Access holes may be provided in the hat section for fastener installation. In addition to the mechanical fasteners, these areas may be sealed to ensure fluid tight design.
Accordingly, it would be advantageous to have a method and apparatus, which takes into account one or more of the issues discussed above as well as possibly other issues.